Pour 2 cups of water into a microwave-safe cup or bowl. I always use a liquid measuring cup.

Microwave it for 2 minutes until very hot. Meanwhile, place pieces of butter into a heatproof bowl or on a plate.

Very carefully remove water from microwave. Place butter in the microwave. Immediately close the microwave door to trap hot air inside.

The radiant heat will soften the butter in about 10 minutes.